The BVDV(Bovine viral diarrhea virus)RNA is ssRNA.After the virus was purified, the BVDV RNA was extracted hy phenol-chloroform-isoamyl aleohl. The DNA contamination in the extracted BVDV RNA was degraded by DNase l. BVDV RNA was further purified by oligo dTcellulose affinity chromotography and agarose gel eleetrophoresis The purified BVDV RNA was polyadenylated at the 3′end under the catalysis of poly A polymerase, eDNA was synthesized with reverse transcriptase using the poly A-tailed BVDV RNA as template...